In surgery, as well as in situations where paramedic personnel are involved, it is commonly necessary to introduce an endotracheal tube into a patient to intubate the trachea and permit the passage of air into and out of the lungs of a patient, thereby aiding in or permitting respiration. During intubation, it is necessary to ascertain that the tube has been properly inserted and has been introduced into the trachea and not into the esophagus.
Paramedics and medical personnel who intubate only occasionally may not be successful in entering the trachea one hundred percent of the time even during visual intubations. Should blind intubation be performed either nasally or orally with the aid of an airway intubator, then the practitioner needs every aid possible to ascertain the correct location of the endotracheal tube. If the tube is in the esophagus there is no return of CO.sub.2 and if it is in the trachea, CO.sub.2 will be present up to about 5% concentration.
There are several conventional methods of diagnosing the correct placement of an endotracheal tube, such as listening to both sides of the patient's chest with a stethoscope; listening to the abdomen of the patient for air entering the stomach; pressing on the patient's chest and feeling the air coming up the endotracheal tube; seeing condensation on a transparent tube; using quantitive analyzers; and cyanosis during I.P.P.V. with an enlarging distended abdomem (Late sign).
Quantitive analyzers provide accurate readings of the carbon dioxide level but they are expensive and bulky for a practitioner to carry around especially when all that is required is an indication as to whether or not CO.sub.2 is present.